ios - 更新后在 Firebase 中查找项目的旧值

Question

我正在制作一个简单的应用来使用 Firebase 进行 CRUD 工作 - 添加、更新和删除。我已完成所有这些任务，但我遇到了更新问题。

在更新子值时，我能够获取对正确用户的引用，并在 Firebase 控制台中成功更新它。这是我使用的代码:

 let ref = FIRDatabase.database().reference().child("Users")
    ref.observeEventType(.ChildAdded, withBlock: { (snapshot) in

        guard let dictionary = snapshot.value as? [String:AnyObject] else { return }

        if self.firstNameField.text == dictionary["firstname"] as? String
        {
            if let lastname = dictionary["lastname"]
            {
                print("Here is the lastname of the current person \(lastname)")

                guard let firstname = self.firstNameField.text, lastname = self.lastNameField.text, dateOfBirth = self.dateOfBirthField.text, zipcode = Int(self.zipcodeField.text!) else
                {
                    print("Form not valid")
                    return
                }

                let properties: [String: AnyObject] = ["firstname": firstname, "lastname": lastname, "Date of Birth": dateOfBirth, "Zipcode": zipcode]

                let currentKey = snapshot.key
                ref.child(currentKey).updateChildValues(properties, withCompletionBlock: { (error, ref) in

                    if error != nil
                    {
                        print("We have an error updating the data \(error)")
                    }

                    print("We were able to update the entry in the reference \(ref)")

                })
            }
        }

    }, withCancelBlock: nil)

我的问题是，当我关闭 EditViewController 后，TableViewController 不会立即更新正确的索引。 tableview.reloadData() 方法对此不起作用，所以我认为我需要在 ChildChanged 方法中修复它。这是代码:

ref.observeEventType(.ChildChanged, withBlock: { (snapshot) in

        print("One of the entries were changed so we're reloading the table view")

        if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname")
        {
            let fullname = "\(firstname) \(lastname)"
            self.names[I_Need_This_Index] = fullname
            print(fullname)

            dispatch_async(dispatch_get_main_queue())
            {
                self.tableView.reloadData()
            }
        }

    }, withCancelBlock: nil)

上面的代码位于一个名为observePeople()的方法中，该方法在viewDidLoad方法期间被调用。 observePeople() 方法处理 ChildAdded、ChildRemoved 和 ChildChanged 通知。

如何正确导航到旧索引并将旧值更改为新值，以便 TableView 正确更新？

Answer 1

这是我的一个临时解决方案，它只能工作一次，之后就不再工作:

我创建了一个名为“ogFullName”的全局字符串变量，并在子添加代码期间将其设置为全名。然后在我的 child 更改的代码中，我将“ogFullName”设置为我要更改的元素的索引。对我来说用语言解释有点困难，所以这是代码:

var ogFullname:String?

func observePeople()
{
    let ref = FIRDatabase.database().reference().child("Users")
    ref.observeEventType(.ChildAdded, withBlock:
    { (snapshot) in

        if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname")
        {
            let fullname = "\(firstname) \(lastname)"
            self.ogFullname = fullname //the old name
...

在我的 ChildChanged 代码中:

 ref.observeEventType(.ChildChanged, withBlock: { (snapshot) in

        print("One of the entries were changed so we're reloading the table view")

        if let firstname = snapshot.value?.objectForKey("firstname"), lastname = snapshot.value?.objectForKey("lastname")
        {
            let fullname = "\(firstname) \(lastname)"
            if let ogname = self.ogFullname
            {
                if let originalIndex = self.names.indexOf(agnate) //finding the index of the unchanged name
                {
                    self.names[originalIndex] = fullname //setting the old name to the changed one
                }

此解决方案每次构建只能运行一次。之后，它会继续在控制台上显示更新的相同行为，但不在 TableView 上显示。